全文获取类型
收费全文 | 2653篇 |
免费 | 70篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 54篇 |
综合类 | 2篇 |
化学工业 | 545篇 |
金属工艺 | 88篇 |
机械仪表 | 62篇 |
建筑科学 | 32篇 |
矿业工程 | 3篇 |
能源动力 | 168篇 |
轻工业 | 116篇 |
水利工程 | 27篇 |
石油天然气 | 17篇 |
无线电 | 297篇 |
一般工业技术 | 648篇 |
冶金工业 | 320篇 |
原子能技术 | 18篇 |
自动化技术 | 337篇 |
出版年
2023年 | 25篇 |
2022年 | 70篇 |
2021年 | 86篇 |
2020年 | 63篇 |
2019年 | 52篇 |
2018年 | 79篇 |
2017年 | 76篇 |
2016年 | 81篇 |
2015年 | 44篇 |
2014年 | 95篇 |
2013年 | 162篇 |
2012年 | 108篇 |
2011年 | 155篇 |
2010年 | 114篇 |
2009年 | 141篇 |
2008年 | 104篇 |
2007年 | 92篇 |
2006年 | 75篇 |
2005年 | 67篇 |
2004年 | 49篇 |
2003年 | 58篇 |
2002年 | 45篇 |
2001年 | 46篇 |
2000年 | 41篇 |
1999年 | 39篇 |
1998年 | 68篇 |
1997年 | 60篇 |
1996年 | 44篇 |
1995年 | 44篇 |
1994年 | 44篇 |
1993年 | 38篇 |
1992年 | 22篇 |
1991年 | 30篇 |
1990年 | 21篇 |
1989年 | 18篇 |
1988年 | 26篇 |
1987年 | 26篇 |
1986年 | 23篇 |
1985年 | 37篇 |
1984年 | 33篇 |
1983年 | 20篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 23篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 20篇 |
1976年 | 26篇 |
1975年 | 11篇 |
1973年 | 16篇 |
排序方式: 共有2734条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
Cross-layer design: a survey and the road ahead 总被引:25,自引:0,他引:25
Of late, there has been an avalanche of cross-layer design proposals for wireless networks. A number of researchers have looked at specific aspects of network performance and, approaching cross-layer design via their interpretation of what it implies, have presented several cross-layer design proposals. These proposals involve different layers of the protocol stack, and address both cellular and ad hoc networks. There has also been work relating to the implementation of cross-layer interactions. It is high time that these various individual efforts be put into perspective and a more holistic view be taken. In this article, we take a step in that direction by presenting a survey of the literature in the area of cross-layer design, and by taking stock of the ongoing work. We suggest a definition for cross-layer design, discuss the basic types of cross-layer design with examples drawn from the literature, and categorize the initial proposals on how cross-layer interactions may be implemented. We then highlight some open challenges and new opportunities for cross-layer design. Designers presenting cross-layer design proposals can start addressing these as they move ahead. 相似文献
5.
A. K. Srivastava Ram M. Shrestha S. C. Srivastava Rabin Shrestha Dharam Paul 《国际能源研究杂志》2003,27(7):671-685
The power sector in India at present comprises of five separate regional electricity grids having practically no integrated operation in between them. This study analyses the utility planning, environmental and economical effects of integrated power sector development at the national level in which the regional electric grids are developed and operated as one integrated system. It also examines the effects of selected CO2 emission reduction targets in the power sector and the role of renewable power generation technologies in India. The study shows that the integrated development and operation of the power system at the national level would reduce the total cost including fuel cost by 4912 million $, total capacity addition by 2784 MW, while the emission of CO2, SO2 and NOx would be reduced by 231.6 (1.9%), 0.8 (0.9%), 0.4 (1.2%) million tons, respectively, during the planning horizon. Furthermore, the study shows that the expected unserved energy, one of the indices of generation system reliability, would decrease to 26 GWh under integrated national power system from 5158 GWh. As different levels of CO2 emission reduction targets were imposed, there is a switching of generation from conventional coal plants to gas fired plants, clean coal technologies and nuclear based plants. As a result the capacity expansion cost has increased. It was found that wind power plant is most attractive and economical in the Indian perspective among the renewable options considered (Solar, wind and biomass). Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
6.
7.
Guest Editors' Introduction: Overview of Sensor Networks 总被引:4,自引:0,他引:4
Wireless sensor networks could advance many scientific pursuits while providing a vehicle for enhancing various forms of productivity, including manufacturing, agriculture, construction, and transportation. 相似文献
8.
Hemant Ramaswami Atul Modi Sam Anand 《The International Journal of Advanced Manufacturing Technology》2007,31(9-10):857-870
In the wake of growing importance for quality and the need to reduce inspection costs simultaneously, the need for a scientific method of selecting an optimum inspection strategy for coordinate measuring machine (CMM) based inspection has become very important. The inspection error resulting from CMM inspection is greatly affected by the profile irregularities and the sampling strategy, which includes sample size, sampling methods, and algorithms used for form evaluation. This paper describes a system that can recommend an optimal inspection plan based on the needs of the user. A design of experiments (DOE) based approach is used to relate the inspection error with sampling strategies. Surface irregularities are included in the form of lobes formed on the profile. A new two-way model is proposed that works in both directions between the sampling strategy and the performance metrics. The results indicate that the number of lobes and the sampling method used have little impact on the inspection error, while the sample size and form evaluation algorithms have a significant influence. An inspection plan advisor is presented, which provides an inspection plan based on the estimated shape and acceptable measurement error. 相似文献
9.
Rao R. Srivastava A. Blaauw D. Sylvester D. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2004,12(2):131-139
We develop a method to estimate the variation of leakage current due to both intra-die and inter-die gate length process variability. We derive an analytical expression to estimate the probability density function (PDF) of the leakage current for stacked devices found in CMOS gates. These distributions of individual gate leakage currents are then combined to obtain the mean and variance of the leakage current for an entire circuit. We also present an approach to account for both the inter- and intra-die gate length variations to ensure that the circuit leakage PDF correctly models both types of variation. The proposed methods were implemented and tested on a number of benchmark circuits. Comparison to Monte Carlo simulation validates the accuracy of the proposed method and demonstrates the efficiency of the proposed analysis method. Comparison with traditional deterministic leakage current analysis demonstrates the need for statistical methods for leakage current analysis. 相似文献
10.
Davoodi A. Khandelwal V. Srivastava A. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2004,12(10):1066-1075
In this paper, we propose a novel, empirical, and parameterizable model for estimating the probability distribution of wire length for each net in a placed netlist. The model is simple and fast to compute. We did extensive experimentation with state-of-the-art commercial (Cadence) and academic (Parquet and Labyrinth) tools and validated our model. Our distribution model was around three times more accurate than assuming half-perimeter bounding box as the fixed net-length estimate. Since the model is parameterizable it can be easily tailored for different routing tools and benchmarks. This model would be very useful in defining a full fledged probabilistic design automation methodology in which various design metrics are optimized from a probabilistic point of view. We also discuss the application of our model in a novel probabilistic approach to the buffer insertion problem. 相似文献